Instituto de Química e Geociências, Universidade Federal de Pelotas, 96010-610, Pelotas, RS, Brazil.
Anal Chem. 2010 Mar 1;82(5):2155-60. doi: 10.1021/ac902976j.
A procedure for sample digestion based on focused microwave-induced combustion (FMIC) is proposed. This system was developed using a commercial focused microwave oven with a lab-made quartz sample holder and a modified glass vessel. Oxygen flow was used to start and support the combustion. A botanical sample was used to evaluate the operational conditions for further Al, Ba, Ca, Fe, Mg, Mn, Sr, and Zn determination by inductively coupled plasma optical emission spectrometry. Pelletized samples were positioned on the quartz holder, and 50 microL of 6 mol L(-1) NH(4)NO(3) solution was added as igniter. Combustion was completed in less than 2 min, and the temperature was higher than 950 degrees C. The use of a reflux step, the position of sample holder inside the vessel, sample mass, ignition and combustion time, oxygen flow rate, and condenser type were evaluated. Results were compared with those obtained by focused microwave-assisted wet digestion and by high pressure microwave-assisted wet digestion. Agreement of 95-103% was obtained for certified reference materials digested by FMIC (reflux step with 10 mL of 4 mol L(-1) HNO(3)). With the proposed procedure, a complete sample decomposition (residual carbon content lower than 0.5%) was achieved with low consumption of reagents as only 10 mL of diluted nitric acid was necessary. Low relative standard deviation (lower than 3.8%) was observed and high amount of sample (up to 1500 mg) could be digested that allowed lower limits of detection.
提出了一种基于聚焦微波诱导燃烧（FMIC）的样品消解方法。该系统使用商业聚焦微波炉、实验室自制的石英样品架和改良的玻璃器皿开发而成。使用氧气流来启动和支持燃烧。使用植物样品来评估进一步通过电感耦合等离子体发射光谱法测定 Al、Ba、Ca、Fe、Mg、Mn、Sr 和 Zn 的操作条件。将颗粒状样品置于石英支架上，并添加 50 μL 6 mol L(-1) NH(4)NO(3)溶液作为点火剂。燃烧在不到 2 分钟内完成，温度高于 950 摄氏度。评估了回流步骤、容器内样品架的位置、样品质量、点火和燃烧时间、氧气流速和冷凝器类型。结果与聚焦微波辅助湿法消解和高压微波辅助湿法消解的结果进行了比较。用 FMIC（带 10 mL 4 mol L(-1) HNO(3)的回流步骤）消解的认证参考物质得到了 95-103%的一致性。采用所提出的方法，仅需 10 mL 稀释硝酸，即可实现完全的样品分解（残余碳含量低于 0.5%），试剂消耗低。观察到相对标准偏差较低（低于 3.8%），并且可以消化大量的样品（高达 1500 毫克），从而可以降低检测限。
